Dental prosthesis fabrication

ABSTRACT

A method is disclosed for forming an accurate stone cast from a dental hydrocolloid impression, used for the purpose of prosthetic fabrication, such as dental prostheses. The dental stone catalyst, calcium sulfate dihydrate, is engaged onto the internal surface of set hydrocolloid impression. This catalyst, placed in the area between impression material and wet, mixed stone, will act to hasten the initial setting of dental stone that is in closest proximity to the impression. The result is a stratified set of the stone. Setting of the wet, mixed dental stone occurs first at the impression/stone interface. The setting radiates outwardly, away from the impression/stone interface. The mixed stone better resists distortion upon setting and the resultant set stone cast is more accurate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/878,337 filed Jul. 23, 2007.

FIELD OF INVENTION

This invention relates generally to making better fitting removabledental appliances and indirect dental restorations, and, morespecifically, this invention relates to making accurate stone dentalcasts and models.

DESCRIPTION OF PRIOR ART

Stone dental casts need be very accurate replicas of the dentition. Thecast, along with other exact measurements and guidelines supplied by thedentist, enables the laboratory to make crowns, dentures, partialdentures, and obturators. These items are referred collectively asdental prostheses.

Other special applications, such as oral snoring devices, orthodonticappliances, bleaching trays, and nightguards, and surgical stents, mayalso be prescribed by the dentist and are also made from dentalimpressions.

Once a cast is made, it can be sectioned so that segments can beremoved. Segments representing individual teeth are referred to as dies.The dies are indexed in various ways to give an accurate and reliableplacement in and out of the model base. Some practitioners will refer tothis dental cast with removable dies as a dental model. And they willrefer to the one piece stone pour of the impression as a dental cast.However, many practitioners will still use the term “cast” and “model”interchangeably and do not distinguish between the two terms. Dentalmodels are used in the dental laboratory to create dental restorationswhich ultimately will be delivered to the dentist office. Theserestorations are then cemented into the patient's tooth with a cement,such as zinc phosphate cement. These cemented restorations are referredto as indirect restorations. Examples of indirect restorations wouldinclude inlays, onlays, veneers and crowns.

Conversely, direct restorations are those restorations that are buildupdirectly and incrementally into the patients tooth. Silver amalgams andcomposites are examples of direct dental restorations.

When initiating an indirect restoration for a patient, the dentist willfirst carve the tooth structure into a certain shape. This finishedcarved tooth shape is referred to as a prepped tooth, or simply, thepreparation. After this step of tooth preparation is accomplished,impressions are taken to record the new altered dimensions, that is, amoldable material is impressed upon the tooth and allowed to set.Hydrocolloid materials are sometimes employed for these impressions.

Hydrocolloid contains agar and water. Irreversible hydrocolloid is madeby addition of water to a dry alginate formula. The resultant gel is ina moldable state for a given period of time. While it is in thismoldable state it is impressed onto the mouth structures and heldimmobilized until it sets.

Another agar containing impression material is reversible hydrocolloid.Reversible hydrocolloid is brought to a predetermined elevatedtemperature to form a gel. While the hydrocolloid is in this warmed gelstate it is impressed to the oral structures. This reversiblehydrocolloid is then cooled to final set in the mouth by using watercooled metal trays. Collectively, all of the impression materials cureto the shape of the teeth and mouth. The impression material is removedfrom the mouth, capturing a negative image of the impressed area of theoral cavity.

In the lab, a wet mixture of stone is poured into the impression. Uponhardening, after an hour or so, the resultant dental cast is separatedfrom the impression. This cast may be used as a mold in the process offabricating crowns or other indirect restorations.

Removable appliances, such as dentures and partials and the like, arealso made indirectly, with the use of dental impressions.

The fabricated prostheses are delivered to the patient by the dentist.Any irregularities in the fit of the appliance are located and adjustedby the dentist.

So the process of taking impressions, for the purpose of an indirectapproach, avails the patient dental prostheses.

OBJECTS AND ADVANTAGES

A tremendous problem exists with indirect dentistry. Dental appliancesand indirect restorations seldom have a perfect fit. All mouthappliances, such as dentures, and all tooth restorations, such ascrowns, need varying amounts of chair time to adjust. Distortions mustbe compensated for before finalizing the products.

Indeed, dentures do require multiple appointments to finalize. Andusually, the final outcome is a slight disappointment. Consequently,dentures are usually tolerated by the wearer; dentures are seldom astight fitting as the dentist would prefer.

There are so many steps in the dentist office, along with an equallycomplex arrangement in the laboratory, that dentists believe thesolution for ill-fitting prosthetics, can never be achieved.

Similar to the irregularities associated with dentures, acrylicnightguards also usually end up with a compromised outcome. It is verytime consuming to troubleshoot an ill-fitting nightguard, in fact, manydentists have resorted to a soft inside liner attached to the hardoutside acrylic shell. This laminate design is not so much for patientcomfort, but for ease of delivery. The soft material is very moldableand therefore does not have to be a precise fit to the dentition. Itsinherent conforming shape compensates for fabrication irregularities.However, the soft liner is not as durable and long lasting as all hardacrylic.

Indirect restorations also require refinements. It is difficult tolocate areas of distortions and most dentists allow up to an hour ofoffice time to adjust and cement a crown.

This reality of ill-fitting restorations is best summarized by Sharp, etal. in U.S. Pat. No. 5,911,580. In column 1, they describe the normalprocess of a dentist usually having to adjust an appliance. They writeof the possibility that the final outcome may be that the appliancecannot be adjusted adequately. The appliance sometimes needs to beremade.

Prior art shows that there have been many attempts to identify the causeof ill-fitting crowns. In U.S. Pat. Nos. 6,045,359, 5,478,235, and7,021,929 inventors modify dental impression tray designs. They hope toachieve better bonding between the impression material and the tray.

Although it is true, that a bond is needed to the tray, any severedefect such as tray separation would create a gross discrepancy in fitof final appliance. These separations are usually evident to thepractitioner at the time of tray removal from the oral cavity.Impression tray design alone has never made a further refinement in thefit of our dental castings.

Inventors of prior art have attempted to create new impression materialsto increase accuracy. In U.S. Pat. Nos. 6,861,457 and 5,907,002 Kamohararecognizes the inaccuracies associated with polyether impressionmaterial. He further isolates the problems of inaccuracy to impressiontray removal. He feels that recovery from deformation applied duringtime to remove the impression causes dimensional instability. He feelsthe solution for ill-fitting crowns is a more accurate impressionmaterial.

With all of the impression materials on the market today, including thenew ones introduced by Kamohara, there is very little improvement in thereliability of indirect dentistry.

Some inventors believe the inaccuracies occur after the impression iscompleted. They feel distortion occurs in the modeling process. This isthe case with inventor Singer in U.S. Pat. No. 6,149,426. He states thatinaccuracies occur with the master cast. His prior art confirms that theprosthetic must be fitted and corrected several times before it becomesaccurate. He further feels that the problem, however, exists in theplastic trays used in the profession as well as subsequent modeling ofthe impression. His invention does not yield a better fitting crown.

Some inventors attribute a smooth stone cast and easy separation of theset cast from the impression as indications of accuracy. This is thecase in two U.S. Pat. Nos. 5,907,002 and 3,620,778. Present day dentalcasts are distorted due primarily to shrinkage. Any reference to easyseparation of dental cast would have this inventor immediately equate todental cast shrinkage. Most casts today exhibit distortion due toshrinkage.

In U.S. Pat. No. 5,417,750 Cohen and Musikant includes calcium sulfatein his alginate impression material. This is also true with inventorsWatanabe and Kamohara in U.S. Pat. No. 6,509,390. Most alginate formulasrely on addition of calcium sulfate to alginate formulas to act as acatalyst and binder for set and strength of alginate. Calcium sulfateforms a cross link with the alginate material. These alginate formulasare all good performers as impression materials, however the ingredientsof alginate have never acted to cause any type of catalyst effect on thewet, mixed stone poured into and against it. Stone dental casts madefrom alginate exhibit just as great a distortion as with other dentalimpression materials.

Five percent potassium sulfate solution is available from AmericanDental Supply, Inc, Easton, Pa. This product is available to helpcondition hydrocolloid impressions. It may help to provide a smoothercast surface, but does not provide a more accurate cast.

The textbook of PHILLIPS' SCIENCE OF DENTAL MATERIALS states thehydrocolloid may often contain borax additive, which strengthens thegel. Borax is thought to be a gypsum setting retarder. Potassiumsulfate, which is an accelerator, is added to hydrocolloid to counterthe effect of borax. Potassium sulfate is also believed to be a dentalstone catalyst.

However, the potency of potassium sulfate as a dental stone catalyst isunclear to the profession. Many impression materials have incorporatedpotassium sulfate, but none have produced accurate casts. Because thecorrelation between a stratified stone set and cast accuracy is unknown,the effective amount and combination of stone setting catalystingredients remains undiscovered.

Still further, this inventor has used potassium sulfate solution formany years with different hydrocolloids, reversible and irreversible.And this inventor has found no appreciably faster times for setting ofgypsum. Also, even adding the potassium sulfate solution directly to wetmixed gypsum, this inventor could still not verify any difference insetting time as compared to a control mix. And not only setting time,but also, no change in accuracy between potassium sulfate stone mixesversus control mixes could be verified, by this inventor. Significantly,there are no studies, known to this inventor, verifying more accuratecastings using potassium sulfate conditioned impressions.

DENTAL STONE DISTORTION

It is readily accepted in the profession that dental stone distorts uponsetting. Although, it has never been proven how the accuracy of thefinal prosthesis is affected, specifically from the setting stonedistortion.

The stone will either shrink or expand, toward its core center of mass.This uncontrolled distortion causes inaccuracies in the dental cast and,ultimately, in the final dental prosthesis.

Shrinkage of stone toward its center core would cause the areas ofinterest of the dental cast, that is, the areas along the impressionsurface, to pull toward the center of mass, and distort. This distortionwould ultimately lead to inaccurate restorations. This is exactly whatthe profession experiences, without fully appreciating the cause.

Present day technology will pour the impression as a whole, resulting ina die of smaller dimensions than actual. For example, a wax pattern fora crown casting would thus be made from a smaller representation of theactual size of tooth. When the resultant crown is tried onto the tooth,it will be tight. The crown will not fit. It will need to be adjusted.

The mechanism is very different in this discovery. In this disclosure,there exists a stratified set of the stone. Setting of stone firstoccurs closest to the important target areas of the impression. The castis accurate in the target areas of the impression, the areas ofinterest. This is due to the placement of stone setting catalyst.Distortion is controlled. All the expansion or shrinkage of the settingstone occurs peripherally, away from the target areas. Again, this isdue to the stratified set.

The distortion is controlled and will tend to occur in the periphery.Distortion will occur furthest away from the impression surface, whereinaccuracy is less damaging. Thus, indirect restorations and prosthesiswill be formed from more accurate casts, needing less adjustments.Distortion associated with indirect dentistry is the primary reason forgrowth of the use of CAD/CAM in dentistry. In U.S. Pat. No. 6,152,731Jordan et al. describe how dentistry is moving toward digital images.Although digital images are an improvement in efficiency, cost iscertainly a factor. And as far as overall accuracy, the concepts of theenclosed disclosure produce results that rival those of the CAD/CAMsystems.

SUMMARY OF THE INVENTION

A dental hydrocolloid impression is procured in the usual manner, amanner familiar to the dentist. This inventor has found no specificcorrelation to any specific brand of hydrocolloid impression material,or to any specific style of tray design, that effects final outcome.This set impression is placed aside for use in the dental lab.

Subsequently, the dental impression is poured with wet, mixed dentalstone.

When at least partially set, the dental stone cast is removed from thehydrocolloid impression and discarded.

The dental impression is poured again with a second stone pour.

After setting, the second pour cast is separated from the impression andused for prosthetic fabrication.

DETAILS OF THE PREFERRED EMBODIMENT

The basis of this discovery is the fabrication of dental prosthesis froma made from a master dental cast, made from a stratified set of stone.To achieve this, a catalyst in the form of calcium sulfate dihydrate isapplied to the surface of a hydrocolloid dental impression. Calciumsulfate dihydrate is equivalent to set dental stone. Wet mixed dentalstone is then poured into the impression and, thus, into intimatecontact with the stone setting catalyst. This area of wet stone, whichis in direct contact with the catalyst, will begin to set faster, orsooner, than other areas within the mix.

Therefore, the stone sets faster along the impression/stone interfacedue to the direct contact with stone setting catalyst. In a wave-likepattern, layer by layer, the stone sets in a stratified manner. Thesetting starts first at the impression surface and then the settingaction subsequently radiates outwardly, further and further away fromthe impression surface. The catalyst initiates the set in the areas ofstone closest to impression surface. The stone closest to the impressionand catalyst sets sooner, while the areas of mixed stone furthest fromthe impression set last.

Indeed, if the catalyst was not added to the impression surface, rather,added to the stone mix, as an added ingredient to the stone, the entiremix would simply set faster. It would not set in a stratified manner.The final cast would not be more accurate.

Somewhat analogous to the concept of a stratified set is an example ofhow water freezes. In one instance, a cup of water may be placed intothe freezer. The water would freeze as a single mass. It would freeze asa whole.

Present day impression pouring techniques allow for a whole set ofdental stone.

However, water may also freeze on the surface of a lake, due to exposureto cold air. In this instance, water freezes incrementally, radiatingdown, layer by layer, further and further away from the surface, in astratified manner.

This invention discloses a novel approach to control the setting patternof mixed stone. Instead of allowing an entire whole set of stone, theset is controlled to start at the impression surface and advance fromthat point, incrementally, into the remaining wet stone.

If the cast is allowed to set as whole, then the cast will distort to,or, in some cases, away from, its center of mass, depending if the mixedstone were shrinking or expanding, upon setting. Expansioncharacteristics vary for various brands of gypsum. Some manufacturersreport expansion of gypsum products, while other products are held toshrink.

However, adding the catalyst to the surface of the hydrocolloidimpression causes a faster setting of stone immediately adjacent to theimpression surface. The setting action radiates from this point into therest of the stone. The stone gradually sets in a wave-like fashion withthe stone furthest removed from the impression surface setting last.Therefore, any distortion will occur innocently, and unnoticed, in areasdistant from the impression surface.

IMPRESSION MATERIALS CONTAINING STONE SETTING CATALYSTS

Some present day impression materials have stone setting catalysts asingredients. The alginates do mix and set well. However, today'simpression materials do not support a stratified set of stone. In turn,this gives unreliable results in regard to cast accuracy. Stone castsand final end products are no more accurate with these impressionmaterials, as compared to impression materials that do not contain stonesetting catalysts. Of great significance, is the fact, that the bestselling reversible hydrocolloid by the preeminent manufacturer containsno stone setting catalyst.

Four stone setting catalysts are mentioned in the literature. Theseinclude sodium sulfate, potassium sulfate, calcium sulfate, andpotassium titanium fluoride. The inventor has extensive experience withpotassium sulfate used as a setting stone catalyst in many ways. Thiscatalyst has been added to a professionally available formula ofirreversible hydrocolloid, a product that the inventor has used forthirty years. Casts and resultant end dental products have never beenmore accurate that are made from this stone setting catalyst ladenimpression material.

In fact, the inventor has mixed potassium sulfate directly into a wetstone mixture without seeing any difference in setting time as comparedto a control.

In the literature, potassium sulfate is a considered a catalyst only ifused in certain quantities. If this amount is exceeded, then potassiumsulfate becomes a retarder to stone setting. Therefore, this inventorwould consider potassium sulfate a weak catalyst. It may not be asreliable under certain conditions of amounts, varying gypsum formulas,temperature, and other unknowns. The catalyst disclosed herein, calciumsulfate dihydrate, when in direct contact to the mixed dental stone,acts as a strong catalyst, in all instances.

Another brand of irreversible hydrocolloid contains potassium titaniumfluoride. The inventor has personally used this product to produceseveral hundred casts. The resultant casts and final products show noimprovement over other forms of impression systems.

Either there is misconception in our profession concerning catalystswith truly effective stone setting properties or inclusion processes ofthe catalysts into the impression materials is misdirected duringmanufacturing. The science of the addition of catalysts into impressionmaterials is faulted.

In application Ser. No. 11/878,337, it is shown that a suitablecatalyst, potassium calcium dihydrate can be used with unprecedentedresults.

The novel art disclosed in this patent application, demonstrates atechnique to fabricate a dental appliance of unprecedented accuracy. Itis no benefit to the profession simply to add what may be deemed as astone setting catalyst to an impression formula. There is no impressionin today's market that contains an effective stone setting catalyst thatwould actually cause a stratified set of dental stone. There is noimpression today that will yield accurate dental casts or the subsequentfinal dental products made from such casts.

The present day technology of adding stone setting catalyst intoimpressions is not a complete formula for reliable outcome. It is notoperational or complete to give elevated results and, as such, has notbenefited our profession. The knowledge and use, employing presenttechnology, is not available or enabling to the public to produce anaccurate end product.

And since this inclusion of catalyst is part of our manufacturingprocess today, fewer researchers are likely to further evaluate. That isto say, researchers are satisfied with just knowing that stone catalystsare added, that they feel this area of impression dentistry is complete.Due to the processes currently used, and supported by well establisheddocumentation of study, a researcher would be even less likely to lookhere for a solution. They feel there is no need for further study. Thisscenario of complacency only adds more support of Unobviousness.

Unexpectedly, however, to add an effective setting catalyst, and in thecorrect amounts, does reward, producing dental products of unparalleledaccuracy.

The goal is to fabricate an accurate dental appliance, or crown. Only byusing the novelty of this disclosure can this be realized, put intopractice, and produce new results. Never before this invention, wasthere ever a technical effect that was consistently obtained. Until thetime of the present disclosure, the accuracy of indirect dentistry hasbeen very obscure, unreliable, and burdened with much confusion amongthe dental professionals. The dramatic increase of accuracy afforded bythis invention would transcend any inference to anticipation byinherency. The prior art of adding purported catalysts to manufacturerimpression formulas has yet to enrich the public domain. Due to this,the technical outcome has always been sporadic, as one national speakerdescribes: the consistency is “. . . all over the place”. Quality mustbe a consideration when comparing to prior art. In order to beanticipatory, the present day concepts of operation would enable aprofessional to create perfect fitting restorations.

Again, the mere possibility that a certain result may happen and left toan unpredictable outcome and to embellish this present day technique toa level of anticipation in regard to this application isunsubstantiated. There is no natural result nor any degree ofpredictability by what manufacturers have afforded the profession todate. In contrast, the present invention outlines successful outcome.There is natural result flowing from the operation of this disclosure, aresult related to a new technique of using an effective catalyst. Theoutstanding results, that challenge a decades old problem, should beregarded sufficient and the discovery novel and not anticipated.

The PHILLIPS' SCIENCE OF DENTAL MATERIALS textbook goes on to suggestthe incorporation of an accelerator additive, such as potassium titaniumfluoride, into dental impression material. It suggests that this beadded to the hydrocolloid directly to accelerate set time of dentalstone. It is important to emphasize the reason accelerators aresuggested by researchers, is that ingredients such as borax will retardthe setting of stone. If the stone does set satisfactorily, impressionand stone manufactures feel materials are compatible. They do not gofurther to produce a unique product that will definitively set stone,faster than a normal set, closest to the impression material/stoneinterface.

This inventor recognizes the literature has made suggestions to includecatalysts to dental impression materials. Indeed, manufactures haveincluded stone catalysts. Without the catalysts, apparently, either thestone did not set or the stone setting took a very long time. However,manufacturers have never formulated impressions to cause the stone toset faster than the normal set time. No formula causes a stratified setof stone, that is, causing stone to set first, closest to theimpression. Further, no manufacturer had this goal. It is not known thatthe actual effect of a suitable catalyst goes far beyond simply settingof stone, it produces new dimensions of accuracy to the cast.

Dentists, using present day technology, trudge through the process ofdelivering the less than perfect indirect restorations, believing thisis as good as it gets. They feel that the errors we see are a reflectionof the limitations of the accuracies of all the systems involved.Professionals, familiar to the art, believe variables occur cumulativelywith impression distortion, setting of dental stone, waxing techniques,investing and casting, and firing porcelain.

Appreciatively, after time is spent adjusting present day crowns, somecrowns will fit very near perfect. However, some crowns can never beadjusted well enough for clinical acceptance. Crowns that are distortedbeyond clinical acceptance become remakes. Remakes are a disappointmentto dentist as well as the patient. One dental laboratory owner admitshis remake rate is 11%.

To repeat, the goal of this discovery is to fabricate a dentalprosthesis from a master dental cast of stratified set gypsum or stone.This has never been achieved in dentistry. There are no references inour texts or in the U.S. Patent Office relating to stratified set ofdental stone. There may be several tens of different effectivecatalysts. The inventor has used only one, calcium sulfate dihydrate,which is readily available in the dental lab.

Again, consider that impression dentistry is a century old and probablysoon to phase out entirely due to advances of CAD/CAM technology. Thevery unlikely discovery shared herein should not be limited to aparticular kind of dental catalyst. Many types of catalysts would yielda cast of stratified set. However, to date, no one has implemented anyeffective stone catalyst contained within hydrocolloid impressionmaterial. Stratified setting of dental stone remains undiscovered.

Traditionally, dental impressions are poured to completely fill the areaof teeth with mixed stone. Upon setting, this entire pour will shrink toits core. This shrinkage will cause a stone cast to have miniaturizedteeth. These casts are inaccurate.

Any prosthesis, fabricated on such a distorted cast, will also bedimensionally inaccurate. Consequently, about ninety percent of ourindirect restorations, such as crowns and bridges, need to adjustedchairside. Removable prosthesis, such as dentures and nightguards, alsoneed significant adjustment.

These restorations must be adjusted to compensate for the distortion ofa traditional pour of dental stone. A traditional pour fully fills atleast the tooth portion of the dental impression with gypsum andtherefore allows distortion of stone upon its setting.

A stratified set of stone would create a cast with accuraterepresentation of the dentition. Fabrication of prosthesis, using anaccurate cast, produces a better fitting product. These appliances needlittle adjustment and aid efficiency in our indirect dentistryprocesses.

SECOND POUR OF IMPRESSION

Present art determines that the most accurate cast is from the firstpour of the impression. In use, the laboratory technician may elect toduplicate the original master cast with an impression of the master castand work off this duplicate cast to fabricate the final dental products.In other words, he works and fabricates from this copy of the originalcast. This technique is practiced mostly, in the matter of acrylicfabrication.

The laboratory technician will work with this duplicate cast, notknowing, that, although it is an accurate reproduction of the mastercast, it is not accurate of the actual dentition. The second castpossessed microscopic fragments of set stone on its surface, transferredthere from being in contact with the master cast.

The duplicate cast had the benefit of an effective stone settingcatalyst on the impression surface. The catalyst was picked up from theimpression being in direct contact with the original stone cast. Smallamounts of surface stone becomes imbedded into the impression. Due tothe presence of this catalyst, a stratified set will occur when mixedstone is added to pour a cast. So, although the second/duplicate cast isan accurate reproduction of the first cast, it replicates the sameirregularities of distortion as the first cast, and so it is identicallyinaccurate. The duplicate cast is usually used for fabrication and isdestroyed during the lab processes of deflasking, a term referring tothe recovery of a finished acrylic dental appliance, imbedded withininvestment stone. The fabricated appliance is returned to the original,master cast to be adjusted as close as possible. To be sure, theoriginal cast is inaccurate. Present day pour of the impression does notprovide for a stratified set of stone.

Unwittingly, the technician continues the art of fabrication oninaccurate casts. This current exercise, of fabrication using inaccuratecasts, has perpetuated the entire span of impression dentistry.

Although the technician does utilize a stratified cast for his duplicatecast, the profession does not realize that the original cast must be astratified set of stone, for greater accuracy. The claims attachedherein specify attaching the catalyst to set impression material. Itdoes not claim the attachment to unset hydrocolloid. The technicianalready achieves this.

The difference of attaching catalyst to set material has significance.The master cast would be accurate from such a process. Picking upcatalyst into unset hydrocolloid would only enhance accuracy of aduplicate cast.

Since the true accuracy of the stratified set of stone is unknown to theprofession, details to assure best outcome are not adhered to. Forinstance, the principles of using clean mixing bowls and spatulas arenecessary to assure a consistent outcome. This is because any errantfragment of set stone could be incorporated at any site within the stonepour and would act as a stone setting catalyst. Any initial set ofstone, caused by an errant seed of stone catalyst, away from theimpression surface, would cause cast distortion.

Therefore, it is not sufficient to merely state that a second pour castis accurate without full attention to the stated various parametersinfluencing accuracy upon stone setting. Although a stratified set ofstone is possible by duplication of a cast, no one is knowledgeable toapply this principle for optimum results.

The refinements of pouring an accurate second pour cast for reliableaccuracy are not always followed in today's art. The profession todaypours them in a haphazard way, not realizing or utilizing them for thereliable outcome they would be capable of. Again, the disclosure hereinis unknown to the profession and the accuracy of a second pour is yetundiscovered.

Therefore, although second pour casts are not new to the profession, thehandling and production techniques have never been refined to enhanceaccuracy and reliability. Second stone pour casts, poured directly againinto the original impression, have never been used for fabrication; theyhave never produced better dentistry or elevated the profession.

Moreover, as stated above, the fact that present day second pour castsare not poured with great attention to detail leads to a somewhatunreliable replication. Complete accuracy may not be assumed.Anticipation by inherency may not be established by probabilities orpossibilities. In reference to the Oelrich case: “The mere fact that acertain thing may result from a given set of circumstances is notsufficient. If, however, the disclosure is sufficient to show thenatural result flowing from the operation as taught would result in theperformance of the questioned function, it seems to be well settled thatthe disclosure should be regarded as sufficient.” (In re Oelrich, 666F.2d 578,581 ((CCPA 1981)) ((Rich, J.)))

The disclosed method of this patent application produces a very uniqueend product. An accurate cast has a definitive role with the need fordimensional stability carrying forward to further events and processesoccurring both within the lab and within the dentist office. Theaccurate cast itself is not the final product inferred by thisdisclosure; the final product is the appliance or crown delivered to thepatient by the dentist. This new invention enables the well fittingadaptation of an end product, dental appliances.

Anticipation cannot occur unless a prior art reference is enabling. Anyperson today, skilled in the dental profession, would be unable to makeor construct to the final end result an accurate dental appliance. Theywould not possess the operative techniques and practical informationneeded to form accurate final products. No technique presently engaged,or disclosed prior art disclosure of any kind, can be relied on asreference; no technique may be relied on as anticipation for the finalexcellent results of accurate fitting restorations. This long overduesolution to a decades old problem is not anticipated, even by those whooccasionally make second pour casts, and yet fail to know thesignificance and cannot implement to final end processes.

Moreover, this is not just a process for producing products ordinary tothe profession. The results of this invention enable products withaccuracy never before available to our society. This inventionconstitutes revelation, setting a new order of magnitude. The discoverypresents a new standard of care.

HYDROCOLLOID

Dental stone setting catalysts have been added to some hydrocolloidmaterials. Calcium sulfate dihydrate is generally included within theirreversible hydrocolloid (alginate) ingredients. It is added as thereactor:

2NA₃PO₄+3CaSO₄>Ca₃(PO₄)+3Na₂SO₄

Calcium sulfate dihydrate is added as the reactor. However, there is notenough of this catalyst at the impression surface to avail itselffurther as a stone setting catalyst. Significant, is that the stonesetting catalysts contained within hydrocolloid impression materialshave never been formulated to cause a stratified set of dental stone.

No formulation of stone catalyst added to hydrocolloid impressionmaterial has ever caused a stratified set of dental stone. Because ofthis, stratified setting of dental stone is unknown to our profession.

Catalysts have historically been incorporated into certain mixtures ofhydrocolloid. Further, these catalysts have been added to counter theside effect of other ingredients, such as borax, which tend to retardstone setting.

Catalysts have never been added in an effective manner to initiate astratified set of dental stone. There has never been a recipe forsuccess to form a more accurate cast. There is no operative that existsfrom any hydrocolloid to direct any practitioner or researcher toimprove upon the science of adding catalysts. Due to this, the conceptof a stratified set of stone not found in our literature. No patentdiscloses a stratified set of dental stone.

This present application discloses the concept of adding additionalstone setting catalyst to the set impression surface, beyond what isalready present within the alginate formula.

Enclosed herein is a supportive letter volunteered by Dr. Steven LHarris. He is the only dentist applying the concepts described herein.

Also attached is a signed affidavit signed by the applicant.

CONCLUSIONS, RAMIFICATIONS AND SCOPE OF INVENTION

Implementation of this discovered technique enables dental impressionsto yield more accurate casts than present day technology.

This distinctive invention advances dental restorations beyond presentart and the discovery improves the overall standard of care.

Accuracy, to this level, has never been appreciated in dentistry. Thisdisclosed technique will add normalcy and stability to a process that,heretofore, is far from predictable. This new technique is the answer towhat may be the last major challenge in our profession.

To be able to reduce procedural time significantly is not to beunderstated. This technique will not only cut delivery time for thedentist, it produces a better product. Patients will enjoy restorationsthat will feel better and last longer.

Hopefully, a generic catalyst would be produced that would not be stonetype specific. This catalyst could be made available for use that wouldbe compatible with all dental stones. This inventor has not yet studiedall the various combinations of catalysts used with different brand andtype dental stones.

One embodiment of the technique described herein, is to directly applycalcium sulfate dihydrate powder onto the surface of the alginate.Enough catalyst would be absorbed into the alginate to initiate stonesetting. This is a direct application.

The calcium sulfate dihydrate could also be burnished into theimpression surface with an artist's brush. This burnishing action wouldhelp imbed the catalyst crystals into the impression surface. This isalso a direct application.

In addition to the powdered form of catalyst described herein, a dentalstone catalyst could be made available in a liquid slurry form. Such aliquid product would allow for a dipping of the hydrocolloid impression.The liquid will penetrate into the impression, only to leave a thinCalcium sulfate dihydrate precipitate coating on the impression materialto act as a dental stone catalyst.

Another embodiment for this discovery would be to simply pour a secondcast after the original cast is poured. The original cast can bediscarded. The purpose of this first stone cast would be to leave alayer onto the impression surface of calcium phosphate dihydrate toserve as catalyst for a subsequent stone pour. Unobvious to even thoseexpert in the art, the second cast retrieved from the impression will bedimensionally different from the first cast; it will be more accuratecast than the first cast.

Another instance when a second pour may be utilized is with acrylicappliances. The appliance is fabricated upon a duplicate, or second pourcast. The appliance is then finished to the master cast.

The second pour technique is especially compatible with hydrocolloidimpression material, as compared to elastomeric impression material. Thewet, mixed stone is more likely to be absorbed within the hydrocolloid,due the water content of both stone and impression material. Setdihydrate stone is imbedded into the hydrocolloid surface, ready to seedthe set of the subsequent pour. Calcium sulfate dihydrate serves as anexcellent stone setting catalyst.

The end result of this discovery is that all indirect restorations fitwith 90% more accurate. Partly because of the limitations of present daytechnology of pouring casts, we are now turning toward a digital worldof CAD/CAM indirect restorations. These machines are very expensive, andstill have limitations. They cannot make a custom shaded crown, whichmay be necessary to match a single maxillary anterior tooth. This is aserious drawback in today's esthetic conscious world. And the CAD/CAMmachines cannot make dentures, partials, nightguard, or bleaching trays.

This invention has remained undiscovered due to: 1. the complexities ofindirect dentistry, 2. stone setting accelerators have already been usedin impression materials, with no added benefit to cast accuracy 3.second pours, although not used for fabrication, are already performedand are not new to the profession, (although, second pour casts aremade, the mechanism for success is unknown), and 4. lastly, the endresult of a consistent near perfect restoration has, heretofore, neverbeen achieved in dentistry.

The concept of perfect fitting restorations is incomprehensible toexpert professionals. Finding the necessary techniques to accomplishthis would be equally obscure. Please consider that there are over onehundred thousand dentists in this the United States alone, who arefabricating over ten million appliances a year.

This unique disclosure is long overdue. The profession has acceptedstatus quo level of accuracy in dentistry for a very long time.

For over half a century, impression dentistry has remained at statusquo. Consider that dentists have graduated in the fifties, sixties andseventies, practiced an entire career, and retired, without the benefitof accurate restorations. Without the techniques disclosed herein,accurate impression dentistry may have possibly never been realized.With the added incentive of patent protection, the inventor has anopportunity to aid the profession and society. Patients will benefitfrom shorter appointment times and more accurate restorations that willfeel better and last longer.

The Novel Physical Features Of The Claims Provide Enhanced Results AndHence Should Be Considered Unobvious, Making The Claims Patentable UnderSection 103.

The physical distinctions enable greater results. The standard foraccurate impression dentistry is elevated, one which, heretofore, hasbeen unobtainable. Specifically, a method to make more accurate dentalproducts, fabricated from stratified set dental casts, is disclosed,thereby indicating that the physical distinctions are unobvious undersection 103.

The enrichment afforded to our society from this long overdue discoverywould be bolstered by the recognition from all groups and individualsfor its novelty. The knowledge and use of this needed technology wouldbecome available to the public.

A patent incentive may well be needed to direct a new perspective, onebenefiting patients. A patent incentive would help with fasterimplementation and help serve society with improvements that mayotherwise never occur. The ongoing state of indirect dentistry need notcontinue.

REQUEST FOR CONSTRUCTIVE ASSISTANCE

The undersigned has made a diligent effort to amend the claims of thisapplication so that they define novel structure (manufacturers havenever adequately addressed the problems of ill-fitting dentalrestorations) which is also submitted to render the claimed structureunobvious because it produces new results of accurate dental casts andimproved fit of dental restorations (Unobviousness is pointed out overthe existing prior art). If, for any reason the claims of thisapplication are not believed to be in full condition for allowance,applicant respectfully requests the constructive assistance andsuggestions of the Examiner in making constructive suggestions pursuantto MPEP 706.03(d) in order that this application can be placed inallowable condition as soon as possible and without the need for furtherproceedings.

1. An improved method for producing an indirect dental prosthesis,comprising the steps of: a. attaching calcium sulfate dihydrate stonesetting catalyst onto the surface of a set hydrocolloid impressionmaterial; b. pouring a wet, mixed dental stone into said dentalimpression and onto said calcium sulfate dihydrate stone settingcatalyst, whereby the dental stone juxtaposed to said calcium sulfatedihydrate stone setting catalyst sets faster, and further whereby, anaccurate gypsum cast is formed by a stratified set of stone, thereby,enabling accurate restoration or prosthesis fabrication.
 2. A methodaccording to claim 1, wherein said hydrocolloid impression material isreversible hydrocolloid.
 3. A method according to claim 1, wherein saidhydrocolloid impression material is irreversible hydrocolloid.
 4. Animproved method of fabricating dental prostheses, comprising the stepsof: a) attaching calcium sulfate dihydrate onto internal surface of sethydrocolloid dental impression; b) pouring wet, mixed dental stone intosaid dental impression, and into contact with said calcium sulfatedihydrate, whereby, said wet, mixed dental stone sets faster closest tosaid dental impression, and further whereby, a cast of stratified set ofstone occurs; c) fabricate prostheses in usual manner on said cast ofstratified set of stone.
 5. A method according to claim 4, wherein saidhydrocolloid dental impression comprises set dental stone remnant ofcalcium sulfate dihydrate, attached to said internal surface, from aprevious stone pour.
 6. A method according to claim 4, wherein, saidcalcium sulfate dihydrate stone setting catalyst is applied to sethydrocolloid dental impression material by direct application.
 7. Amethod according to claim 4, wherein, said calcium sulfate dihydratestone setting catalyst is applied to set hydrocolloid dental impressionmaterial by immersion into calcium sulfate dihydrate solution.